Increasing Bed Height Research Articles

Textile sludge–sawdust chemically produced activated carbon: equilibrium and dynamics studies of malachite green adsorption

Textile sludge–sawdust chemically produced activated carbon (SSAC) was used in equilibrium and dynamics adsorption of malachite green (MG). The effects of concentration in equilibrium, and influent flow rate (15–30 mL/min), initial concentration (20–80 mg/L) and bed height (2–6 cm) in dynamics mode were investigated. SSAC with surface area of 979 m2/g shows an outstanding maximum capacity of malachite green at 530 mg/g. In adsorption dynamics, the breakthrough time and bed capacity increased with increasing bed height, and decreasing flow rate and influent dye concentration. Bohart-Adams, Thomas, Yoon-Nelson and Clark models were applied to describe the column breakthrough, dynamics behaviour and adsorption mechanisms. The breakthrough curves were best fitted by Yoon-Nelson model at the experimental conditions. The maximum bed capacity was reported to be 565 mg/g. SSAC is an effective adsorbent for MG removal from aqueous phase.

Removal of Cr(VI) and methyl orange by activated carbon fiber supported nanoscale zero-valent iron in a continuous fixed bed column.

The application of activated carbon fiber supported nanoscale zero-valent iron (ACF-nZVI) in the continuous removal of Cr(VI) and methyl orange (MO) from aqueous solution was studied in depth. The breakthrough curves of Cr(VI) in a fixed bed with ACF-nZVI were measured, and compared with those in the fixed bed with ACF. The catalytic wet peroxide oxidation (CWPO) process for MO was also carried out using ACF-nZVI after reacting with Cr(VI) in the same fixed bed. The results showed that the breakthrough time of ACF-nZVI was significantly longer than that of ACF. Higher pH values were unfavorable for the Cr(VI) removal. The breakthrough time increased with decreasing inlet Cr(VI) concentration or increasing bed height. The Yoon-Nelson and bed depth service time (BDST) models were found to show good agreement with the experimental data. The Cr(VI) removal capacity when using ACF-nZVI was two times higher than that when using ACF. Under the optimal empty bed contact time of 1.256 min, the fixed bed displayed high MO conversion (99.2%) and chemical oxygen demand removal ratio (55.7%) with low Fe leaching concentration (<5 mg/L) after continuous running for 240 min. After three cycles, the conversion of MO remained largely unchanged.

Recovery of Pt(IV) from aqueous solutions by spent brewer's yeast‐functionalized zeolite (SBYFZ): A batch and column study

AbstractMineral commodities in Earth's crust, such as platinum, palladium, and gold have to be sustained especially since their ore deposits have been dramatically declining, due to intensive mining, motivated by high demand. The mining of these commodities results in large amounts of wastewater containing traces of precious elements. The current study presents on the recovery of Pt(IV) from aqueous solutions using spent brewer's yeast‐functionalized zeolite (SBYFZ). Batch and column experiments were conducted at different conditions. Two‐ and three‐parameter isotherm and kinetic models were fitted using adsorption data. Pt(IV) was significantly (p &lt; .05) recovered from aqueous solutions within 300 min of contact time, using 10 g/L adsorbent dosage and 2 mg/L at pH 2. The platinum uptake was reduced by 5% when incorporated with adsorption competing ions. Other platinum group elements were successfully removed from aqueous solutions along with Pt(IV). Column studies indicated that breakthrough times were proportional to increasing bed height, highly acidic pH, and low influent concentration. The recovery of Pt(IV) was through mass transfer as concluded from column adsorption models. These results indicated that SBYFZ was excellent for the significant recovery of Pt(IV) from aqueous solutions. Thus, SBYFZ can be used in wastewaters with optimum conditions.

Experimental and computational studies on gas–solid fluidization in a cylindrical column with and without internals

Gas-solid fluidization often suffers from inherent drawbacks like channeling, bubbling and slugging which affect the quality of fluidization. Efforts have been made in this present investigation to improve the quality of fluidization in gas–solid fluidized beds by conducting hydrodynamic studies in cylindrical fluidized bed column with and without internals. The effect of hydrodynamic parameters such as inlet air velocity, bed height and internal spacing on pressure drop, expansion ratio, fluctuation ratio, minimum fluidization velocity and fluidization index were studied. The pressure drop was found to increase with an increase in bed height regardless of presence or absence of internals. But in the presence of Internals (More Number of internals or less spacing) pressure drop initially decreases but beyond a certain level the resistance offered by the internals is more, and it caused a slight increase in pressure drop. The expansion ratio and fluctuation ratio reduces significantly with a decrease in the spacing of internals. The effect of the internals on quality of fluidization has been studied. By the introduction of internals, the quality of fluidization in terms of fluidization index has improved. The experimental data was used in the CFD simulations and the results obtained are in good agreement with the experimental observations. It is found from the simulation results that the bed height increased with increase in air velocity. The solids are more evenly fluidized in the presence of internals with smaller bubble size and lower bed height than the beds without internals.

Exergy analysis and parameter optimization of sinter cooling process in vertical moving bed for waste heat recovery

A steady-state mathematical model is proposed to investigate the sinter cooling process in vertical moving bed, and the optimal parameter combination of vertical tank (VT) is obtained based on the maximum enthalpy exergy of cooling air (EECA) through the method of orthogonal experiment. The results show that, the air outlet temperature increases with increasing the air inlet temperature, bed inner diameter and height, and decreasing the air flow rate. The gas flow pressure drop basically increases linearly with increasing the air flow rate, air inlet temperature and bed height, and decreases exponentially with increasing the bed inner diameter. EECA can reach the maximum value with the increase of air flow rate and air inlet temperature. When the air flow rate exceeds a certain limit value, EECA also has a maximum value with the increase of bed height, while there is not a turning point for the change curve of EECA with the bed inner diameter. Taking the actual annual output of 360 m2 sintering machine as the research object, the optimal parameter combination of VT is 9 m for the bed inner diameter, 8 m for the bed height, 353 K for the air inlet temperature and 180 kg/s for the air flow rate, respectively.

Three-dimensional MP-PIC simulation of the steam gasification of biomass in a spouted bed gasifier

By coupling the heat transfer and chemical reactions, biomass-steam gasification in a lab-scale spouted gasifier is numerically simulated via the multiphase particle-in-cell approach. The proposed model is firstly validated with the experimental results. Then, the spatial distributions of biomass particles, spout-annulus boundary, the gas species, the gas-solid flux, together with the influences of operating parameters are discussed. The results demonstrate that: (i) similar to the well-known Brazil nut effect, density-induced segregation of biomass and sand species results in the accumulation of large-diameter biomass species near the bed surface. High temperature does not change the general distribution of the spout-annulus boundary; (ii) the gaseous products mainly concentrate in the fountain; enlarging the bed height and biomass diameter reduces but increases the mole fraction of CO and H2, respectively. The steam-biomass ratio has a promoting effect on the production of H2, while higher gasification temperature reduces the H2 yield; (iii) enlarging the bed height and steam-biomass ratio decreases and increases the vertical flux of both the gas and solid phase in the dense region, respectively. The increase of bed height and steam-biomass ratio reduces and enlarges the gas voidage, respectively. The results obtained in this work provide meaningful insights regarding the presence of Brazil nut effect induced by the density difference and the complicated multiphase flow in the spouting apparatus, which will be beneficial to the design and optimization of this kind of gasifier.

Removal of Cu(II) ions using bio‐adsorbents in fixed—Bed continuous bed mode—A comparative study and scale‐up design

AbstractThe study presents the removal of Cu(II) ions using bio‐adsorbents. The applicability of the continuous column process using hyacinth root, rice husk, blackberry leaves, and guava leaves is reported in this study. The effects of solution pH were studied in batch mode, and other different process parameters such as bed depth, rate of flow, influent solution concentration were investigated and optimized in the continuous mode. The breakthrough curves were obtained for various initial metal concentrations (10, 20, and 30 mg.L−1), flow rates (10, 30, and 40 ml.min−1), and bed height (4, 6, and 10 cm). The optimum operating conditions were 10 cm bed depth, 10 ml.min−1 flow rate, 10 mg.L−1 influent concentration, and pH 6. The breakthrough time was increased with increasing bed height and decreasing flow rate and influent concentration. The Freundlich isotherm model was in good agreement (R2 = .9247–.9987) with the batch experimental data whereas, the continuous experimental data fitted well in the Thomas model to illustrate the best performance of the fixed‐bed process. FTIR spectra and SEM images verify the sorption capacity of the adsorbents. The Cu(II) adsorption capacities of the adsorbents were compared, and the hyacinth root gives the best result compare to the others. Hence, the results proved the effectiveness of the adsorbents for the removal of Cu(II) ions.

Packed bed column studies of hexavalent chromium adsorption by zinc chloride activated carbon synthesized from Phanera vahlii fruit biomass

In the present work, biosorption potential of zinc chloride activated biomass of Phanera vahlii fruit was investigated for abatement of hexavalent chromium from synthetic solution in continuous mode. Zinc chloride activation provided the activated carbon with large surface area and pore volume. The parameters influencing continuous adsorption process viz. flow rate, bed height and initial metal concentration were considered as 5–15 mL/min, 2–8 cm and 50–200 mg/L, respectively and optimized. With increase in bed height, the breakthrough time increased while with increase in initial metal concentration and flow rate, the breakthrough time declined. It was discovered that the continuous column adsorption models viz. Thomas and Yoon–Nelson fitted better with the experimental data as compared to Adams-Bohart and Bed Depth Service time (BDST). In conclusion, it was discovered that zinc chloride activated Phanera vahlii fruit biomass is a promising adsorbent for adsorption of hexavalent chromium in continuous mode.

Adsorption of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) from water using leaf biomass (Vitis vinifera) in a fixed-bed column study.

Adsorption of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) onto modified activated carbons (AC-H3PO4) produced from leaf biomass of Vitis vinifera leaf litter in a fixed bed column experiment was investigated in this study. The column bed was packed with the produced activated carbons in a uniform particle size of ˃ 64μm. Experimental parameters including the initial concentration of the solution, column bed height, the mass of adsorbent and flow rate were optimized to establish the best adsorption efficiency parameters for the system. Breakthrough and saturated time were estimated from the column fixed bed experimental data and analysed using the Adam-Bohart, Thomas model, and Yoon-Nelson models. Maximum sorption capacities of produced activated carbon ACH3PO4 based on Thomas model were 159.61 and 208.64mg/g for PFOA and PFOS, respectively. The results indicated the breakthrough and saturated time of the system increased concurrently with the increase in bed height and initial concentrations, while an increase in flow rate enhanced fractional bed utilization (FBU) efficiency of the column. Thomas and Yoon-Nelson model best describe the prediction of breakthrough data and sorption behaviour of PFOA and PFOS indicating suitability of AC-H3PO4 column design. Findings suggest that agro based adsorbent is a good alternative to non-ago based adsorbent. The surface characteristics of the phosphoric acid modified activated carbons AC-H3PO4 affirmed the removal of PFOA and PFOS from the contaminated water.

Efficient removal of methylene blue by low-cost and biodegradable highly effective adsorbents based on biomass in the fixed bed column

The adsorptive ability of sustainable biomass (spent coffee ground (SC) and water hyacinth (WH)) and activated biochar derived from WH to remove methylene blue (MB) from aqueous solution was evaluated under continuous fixed-bed column. Morphological structure and functional groups of WH and SC were determined by SEM and FTIR, respectively. The SEM showed the presence of porous structure of WH, whilst FTIR confirmed the presence of more hydroxyl groups at the WH surface, resulting in higher MB adsorption. A series of column experiments were performed with varying bed height and initial MB concentration. To determine the breakthrough curves and characteristic parameters for process design, Yoon-Nelson, Thomas and modified Dose-Response models were applied to experimental breakthrough data. The MB adsorption was dependent on the bed height and initial MB concentration. An increase in bed height resulted in improved adsorption capacity. With increasing initial MB concentration, the adsorption capacity decreased. The maximum adsorption capacity (Q0) of ∼391 mg/g by WH (at 0.75 cm bed height and 300 mg/L initial MB concentration) and ∼393 mg/g by its activated biochar (at 2 cm bed height and 200 mg/L initial MB concentration) was observed. The results showed that WH gave comparable MB adsorption capacity with a greater cost-effectiveness.

Effects of flow behavior index and consistency coefficient on hydrodynamics of power-law fluids and particles in fluidized beds

Flow behaviors of particles and power-law fluids were numerically simulated by means of Euler-Euler model with kinetic theory of granular flow in liquid-solid fluidized beds, and effects of flow behavior index (n) and consistency coefficient (K) were studied. The simulation results were compared with the experimental measurements, and good agreements were achieved. The effective viscosity of the shear-thinning fluid decreases as it flows through the expanded bed due to the increase in fluid strain rate. Unlike the homogeneous distributions of particles in Newtonian liquid fluidized beds, four regions for particle flow were observed along the bed height when a non-Newtonian fluid acts as the fluidizing agent, which indicates the non-uniformity of particles distribution. With the decrease of n, the enhancement of shear-thinning characteristics of the fluidizing agent thickens the relative inlet region and enhances the non-uniformity of particles along the bed height. The increase of n accelerates the circulation of particles in the fluidized bed, which speeds up the renewal of the particulate materials throughout the reactor space. The increase in K increases the apparent viscosity of the fluidizing agent. The bed height increases and the average solid volume fraction decreases. However, the influence of K on the non-uniformity of particles in the bed is less significant than that of n.

A study of lead removal using sargassum tenerrimum (brown algae): Biosorption in column study

The sorption capacity of sargassum tenerrimum powder is studied for various flow rates i.e., 10, 20 and 30 mL/min. The initial pH of aqueous solution is maintained at 5. For the flow rates of 10, 20 and 30 mL/min, the breakthrough times are 32, 26 and 18 min respectively while the exhaust times are 90, 85 and 75 min respectively. The time taken to achieve breakthrough has decreased with increase of flow rate. A glass column having 2.54 cm internal diameter (ID) and length of 40 cm were used. The experiments are conducted for two different bed heights (5 and 10 cm) using 2 and 4 g of biosorbent. A flow rate of 30 mL/min of aqueous solution (Co = 20 mg/L) is maintained. With an increase in bed height, the throughput volume is increased to achieve the saturation and this increase in input volume, would result in higher contact time, thereby increasing the uptake capacity. Lead biosorption uptakes are increased from 13.852 to 20.839 mg/g as the bed height is increased from 5 to 10 cm. the breakthrough curve models BDST, Thomas and Yoon-Nelson models were studied for discussing the fixed bed column onto biosprion of lead.

Performance evaluation of various individual and mixed media for greywater treatment in vertical nature-based systems

Nature-based systems (NBS) are a cost-effective, energy efficient and aesthetically pleasing approach for greywater treatment, but they are space intensive. Vertical NBS overcome this issue but must utilize lightweight media to reduce their construction costs. This study evaluates four common plant growing media: perlite, coco coir, LECA and sand, and compares them with two new media derived from local waste materials: date seeds and spent coffee grounds (SCG). The media are characterized and tested for their removal of various greywater pollutants. Further tests are conducted comparing mixtures of perlite-coco coir and date seeds-SCG. SCG was found to be an excellent media for greywater treatment, providing a similar degree of treatment as the best traditional media, coco coir and providing improved drainage. Drainage was further improved by mixing SCG with date seeds, which performed better than any mixture of perlite and coco coir. Most pollutants showed a slight deterioration in treatment performance with this mixture, although the removal of suspended solids and chemical oxygen demand was improved. An increased bed height improved the treatment performance with SCG, while increased hydraulic loading resulted in decreased treatment performance for all media. This study demonstrates the potential of date seeds and SCG as locally recycled waste materials to realize treatment of greywater in vertical NBS.

Heat transfer and hydrodynamics of particles mixture in swirling fluidized bed

This work is an experimental study of heat transfer and bed hydrodynamic parameters affecting a bed particles-mixture in a swirling fluidized bed reactor. Two different materials (Geldart type- D), polyethylene (PE) beads with a diameter of 6 mm and sand with a mean diameter of 1.5 mm were used as bed materials fluidized by air. Different mass fractions of PE beads (0.25, 0.5 and 0.75) were used. The bed-wall heat transfer coefficient was calculated for different inlet air velocities and different axial heights. Both minimum fluidizing and minimum swirling velocities increased with increasing PE mass fraction. Increasing amount of PE beads increased the pressure drop of the bed. While increasing the percentage of PE beads resulted in decreasing the local heat transfer coefficient. The heat transfer coefficient reduced with increasing bed height for all PE beads mass fraction. The effect of using a central body with a cone shape on the operation of the reactor was also studied. Using a central body with cone shape causes enhancing the heat transfer and bed flow processes as a result of increasing the coefficient of heat transfer and decreasing bed pressure drop.

Low-cost, biodegradable and highly effective adsorbents for batch and column fixed bed adsorption processes of methylene blue

This work reports the preparation of low-cost and ecological bioadsorbents and study of their adsorption properties in the elimination of methylene blue dye (MB) from wastewater Unmodified citrus peels (UCP) and unmodified citrus peels encapsulated with calcium alginate (UCP/A) were characterized by elementary analysis, FTIR, DRX, SEM. Isotherm studies in the batch system were investigated and the maximum adsorbed amounts were found to be 185.83 and 964.54 mg/g respectively for UCP and UCP/A. The Langmuir model fitted well experimental data of isotherms with high coefficient correlation R2, low RMSE and χ2. Fixed bed adsorption was studied with operational conditions such as the bed height, MB flow rate and MB inlet concentration to test the performance of column. The breakthrough curves and the break time increase with the decrease of the rate flow and with the increased bed height. The highest bed capacity of 31.45 mg/g and highest percentage of MB solution treated (93.6%) was obtained using 2 mL/min rate flow, 200 mg/L inlet MB concentration and 3.5 cm (4 g) bed height. The breakthrough curves were fitted using Thomas and Yoon and Nelson models. The behaviors of the breakthrough and the R2 founded by these models are high (R2>0.97) which shows good applicability of models.

A breakthrough column study for removal of malachite green using coco-peat

A continuous adsorption study in a fixed bed column using coco-peat (CP) as an adsorbent was carried out for the removal of toxic malachite green (MG) from contaminated water. Fixed bed column studies were carried out to check field application viability. Various parameters like particle size, pH, concentration, dose and interference were exercised to optimize dye removal. Data obtained from breakthrough column studies were evaluated using Thomas and BDST model. Thomas rate constants Kt (0.22 ml min−1 mg−1) and adsorption capacity qo (181.04 mg g−1) were estimated and found to favor efficiency of CP. Thomas model was tested with several parameters like flow rate, concentration, and bed depth. Upon increase in input dye concentration, flow rate and bed height, adsorption coefficients increased. According to BDST model, maximum dye uptake of 468.26 mg/l was obtained with an input dye concentration of 5 mg/l. HYBRID and MPSD error functions were tested and found that Thomas model fits best. Dilute hydrochloric acid was found best for desorption. Real wastewater from textile industry was analyzed and confirmed the prospect of large-scale industrial application. In conclusion, coco-peat can be used as a promising bio-sorbent in column bed for scavenging of MG from contaminated water.

Adsorption Performance of Packed Bed Column for the Removal of Lead (II) Using Velvet Tamarind (Dialium indum) Shells

The removal of Pb ions by activated carbons prepared from velvet tamarind (Dialium indum) shells was studied to investigate its uptake potentials using column sorption at different operating conditions (flow rates, initial concentrations and bed height). The prepared adsorbent was characterized by determining the physicochemical properties, proximate analysis, carbon, Hydrogen, Nitrogen and Sulpur analysis, Fourier Transform-Infra Red, Potentiometric titration. Different dynamic models were used to describe the sorption processes. The FTIR analysis results suggested the presence of functional groups such as hydroxyl, carbonyl, carboxyl and amine which could bind the metals and remove them from the solution. The values of moisture content, volatile matter, fixed carbon and ash content as obtained from % proximate analysis are 3.43, 27.07, 65.05, 4.45 for activated carbons prepared from velvet tamarind shells. Ultimate analysis revealed that activated carbons prepared from velvet tamarind shells contained 75% carbon. The surface area and Iodine number of activated carbon from velvet tamarind shell are 570 m2g-1 and 614.7 mgg-1 respectively. The column experimental data revealed that an increase in bed height and initial metal concentration or a decrease of flow rate enhances the longevity of column performance by increasing both breakthrough time and exhaustion time thereby delaying bed saturation. Low ash content and high surface areas are indication of good mechanical strength and microporosity of the activated carbons prepared from this precursor. The activated carbons are inexpensive and appeared to be effective and can be explore for future commercial application for environmental sustainability.

A comparative study on dynamic Hg(II) and MeHg(II) removal by functionalized agrowaste adsorbent: breakthrough analysis and adsorber design

The adsorption dynamics of inorganic mercury, Hg(II) and organic methylmercury, MeHg(II) removal by low-cost reactive agrowaste adsorbents namely CP-Pure, CP-MPTES and CP-RR was investigated in a fixed-bed adsorber. The results show that the breakthrough and saturation times were delayed with decreasing flow rate (F) and initial concentration (Co), and increasing bed height (Z). The Hg(II) possessed better adsorption performance than MeHg(II). The isotherm and kinetic model analyses of adsorption data followed the Temkin isotherm and the pseudosecond order kinetic models, respectively. The breakthrough curve was simulated well by the Thomas and Yoon-Nelson models, and then was further used for scale-up studies. The empty bed contact time (EBCT) concept was successfully demonstrated for the adsorber design and scale-up studies. The regeneration studies showed that the regenerated CP-Pure and CP-MPTES have a high regeneration efficiency up to third adsorption cycle.

Photocatalytic degradation of azithromycin using GO@Fe3O4/ ZnO/ SnO2 nanocomposites

Sewage output contains a wide range of organic materials, such as pharmaceutical compounds. These compounds have harmful effects on the environment, such as generation of antibiotic-resistant bacteria; therefore, their degradation has been considered as one of the environmental challenges. The purpose of this research is to synthesize graphene reinforced with nanocomposites of iron oxide/zinc oxide/tin oxide and evaluate its ability to photocatalytic degradation of azithromycin in the aqueous environment. GO@Fe3O4/ZnO/SnO2 nanocomposite was characterized by various techniques including XRD, FT-IR, TEM and VSM. In the batch system, the effect of pH, contact time, catalyst content and initial concentration of azithromycin was investigated; in this system, under optimal conditions of pH = 3, 120 min with 1 g/L of GO@Fe3O4/ZnO/SnO2, 90.06% of 30 mg/L azithromycin were degraded under UV-C irradiation. In the continuous system, the variables of bed height, flow rate and initial concentration of azithromycin have been investigated. The times to reach the column breakthrough point (Cb = 0.02C0) at heights of 6, 8 and 10 cm are 5, 8 and 14 min, respectively. By increasing the height of the bed from 6 to 10 cm, the azithromycin degradation rate increases; the reason for this increase can be due to the increase in contact time. The results indicate that the degradation of azithromycin in a constant bed column strongly depends on these parameters; actually, the time to reach the breaking point decreased with increase of flow rate and initial concentration of azithromycin while increasing with increase of bed height. Estimating the empty bed residence time showed that this model is in good agreement with laboratory data. Therefore, considering the high ability of GO@Fe3O4/ZnO/SnO2 to eliminate azithromycin, this compound can be used as an effective catalyst for the degradation of antibiotics in aquatic environments.

Column Efficiency of Fluoride Removal Using Quaternized Palm Kernel Shell (QPKS)

In this research, the adsorption potential of quaternized palm kernel shell (QPKS) to remove F−from aqueous solution was investigated using fixed-bed adsorption column. Raw palm kernel shell waste was reacted with 3-chloro-2-hydroxypropyl trimethylammonium chloride (CHMAC) in order to modify the surface charge. The effects of inlet F−concentrations (2–12 mg/l) and QPKS bed height (2–10 cm) with optimum pH (pH = 3) on the breakthrough characteristics of the adsorption system were determined. In the fixed-bed column, breakthrough time increases with increasing bed height due to increasing amount of active site on adsorbents to adsorb the fluoride ion. Decreasing trend of breakthrough values was obtained with increasing initial fluoride concentration due to greater driving force for the transfer process to overcome the mass transfer resistance in the column. The adsorptions were fitted to three well-established fixed-bed adsorption models, namely, Thomas, Yoon–Nelson, and Adams–Bohart models. The results fitted well to the Thomas and Yoon–Nelson models with correlation coefficient,R2 ≥ 0.96.